The objectives of this work are to investigate the separate contributions of the retinal and choroidal circulations to retinal tissue oxygenation and to evaluate a newly developed angiographic technique for evaluation of the choroidal circulation in man. Using micro electrodes, tissue pO2 maps will be made of the various retinal and choroidal layers of the living primate eye. These maps will be made under physiologically normal conditions of ocular circulation, with occluded retinal circulation, occluded choroidal circulation, and with and without hyperbaric oxygenation of arterial blood. To make this mapping possible, exposed Pt tip microelectrodes are used in conjunction with a polarographic technique designed to permit quantitative tissue pO2 measurements by application of the polarization potential for less than 50 m sec. Further clinical evaluation of the multispectral fundus camera will be made. Following a simple intravenous injection of a sodium fluorescein and indocyanine green dye mixture, this camera optically separates light returning from the eye in such a way that the separate retinal, choroidal arterial and capillary, and choroidal venous circulations are simultaneously photographed. A number of choroidal angiograms from normal eyes have been made, and these will be compared to choroidal angiograms from eyes with various known diseases.